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MHR University - Defensive Line Substitutions

It is no small thing to make a substitution on the field of play. At the pro level, offensives have been known to watch for slow, lumbering defensive tackles to head to the sideline, at which time the offensive to quickly races to scrimmage to catch the defense with an extra man on the field.

Offenses like to prey on defensive lines by hitting them with run blocks and calling no huddle plays to keep big defensemen worn down. And even without an offense focused on wearing down the DL, those big guys on the defense are going to be hurting as the game goes on.

How do defenses counter these threats, and what goes into defensive substitutions? Well, I'm glad you asked. This week's University story is all about how defenses counter the offense's attempts to wear them down. More after the jump...

Endurance Training is a Major Key

So much time in football is devoted to strength training, technique training, and learning plays that endurance is sometimes set to the side. Great fourth quarter teams are teams built on endurance. If your opponent is sweating, puking, and spending time between plays with his hands on his knees, the game is won.

Exhaustion is not only a physical disadvantage. Exhausted players don't think as quickly since valuable oxygen is being routed to major muscle groups that are starving. A player that feels sick and tired has to expend some mental energy towards gearing himself up for the next play instead of focusing on the issues that will win his part in the bigger game.

About two and a half years ago I wrote an article (link) about the imporance of endurance. I won't copy the entire article here, but I'd like to copy a portion that explains why endurance training becomes the "equalizer" for a defense.

Here, I explained why offenses don't wear down as fast as defenses. I then conclude with the impotance of endurance training.

The first reason is that offenses have the advantage of knowing what is coming and get to commit to a direction of movement first. In contrast, a defense not only doesn't know the snap count (so they have a slight disadvantage having to focus on the ball), but doesn't know in advance how the play is supposed to unfold. The defensive player is thus typicaly in a stance whilst physicaly tense for the entire count, and then has to commit to a direction of play often having to change direction as they see their responsibilities change as the play moves on.

Second, imagine being a heavy lineman and not knowing whether you will have to penetrate for a pass rush or having to tackle if the play turns into a run. Either way, you very well might be about to get pounded by an offensive line knocking you on your butt on a run play. The offensive line doesn't have the same guess work. They already know if they will be doing the hitting or the pass blocking.

The QB and receivers even know where the ball is supposed to go. The CBs have to keep with their guys and react (which takes more energy than running a route from memory like a receiver does).

Endurance is the equalizer for a defense. If you have depth you can rotate in guys, but not if the other team goes no huddle. Endurance allows replacement players to stay on the bench longer, and allows starters to recover and get back in the game more quickly.

With the high school team I coached defense on (like any high school program in the country) we were severely (but correctly) limited against much training or even conditioning in the off season. However, we encouraged kids to come to camp in shape by requiring a 4 mile run on the first day. It wasn't a deal breaker by itself, but it was one of the biggest things we looked at. A kid didn't have to be Bruce Jenner; he only needed to go four miles without stopping or walking. A snail-like jog was all we asked. Again, this test wouldn't wipe a kid out automaticaly, but it might. Kids wanting to make our program could be found around town jogging each day. This helped us go into the early season with an advatage that is hard to describe if you didn't see it for yourself.

System Based Counters to Exhaustion

Based on what kind of team an offense faces (and the build of the defensive players), the offense may attack the team with the intent to wear them down. This may include running plays and no huddles. Are there defenses that naturaly counter these?

The obvious answer is to have smaller players. Smaller players recover better from cardio-vascular punishment. But in any case, a bend don't break system is a powerful counter.

In the bend don't break, several factors come into play. First, with less attacking from our defense, the players are able to play more within their own space, instead of executing the energy needed to invade the opponent's space. Second, the defense trades space (in terms of short yards given up) for opportunities. The more plays that the offense runs, the better the chance that they make a major mistake (a fumble, an INT, a failed third down conversion, etc).

While not a system based approach, a team can also scheme against no huddles. An effective scheme is to have three or four simple plays that can be run by the defense (called randomly by the MLB) so that time is saved and the responsibilities of more complex plays are tossed aside.

The Time Out

Coaches hate to call a time out when the opponent is going no huddle. Many coaches see a time out as an admission of weakness, or a major concession. Indeed, sometimes a time out is exactly what the other team wants.

On the other hand, a TO may be lesser of two evils and sometimes it may even be for the best. The key here is for the coach to think with a level head and weigh the loss of a TO against the entirety of the game, not just the current drive.

The Substitution

There are two ways to substitute. One way is the "rotation", in which we keep players fresh by rotating them on and off the field (much like we see in hockey "line changes"). The other way is a straight substitution (where a player either signals that he is winded or the staff sends in the change).

Both methods are fraught with danger.

Substitute too often, and the players get gassed justnning on and off the field. Done too rarely, and the other team will call in the no-huddle just before the switch. Done too regularly, and the opponent learns to time his no huddle. If a signal for a switch is too obvious, that player will be left on the field to be attacked.

The best approach is to use a combination of rotations and straight substitutions. At the HS level, opposing coaches will pounce on a young player's mistakes, but at the pro level a player should know exactly when and how often to pull himself from the field (his reserve should be waiting for the moment). This is best done at the moment of the whistle, while keeping an eye out for 1) a quick no huddle and, 2) assurance that the reserve player is on his way in.

In our program, when the defense was on the field our OL coach was watching the line to see where we were having problems and to see what the OL was doing (our DL coach watched our OL and the opponent's DL). He made the call on substitutions based on mis-matches and who looked tired.

The key in pulling a player is to pull them well before they are tired. This point is where some of the biggest mistakes are made in coaching. If you wait to pull a player until he is tired, he has likely already been playing at a lessened level. Second, the team could now get caught in a situation where it is harder to substitute (either because of the no -huddle or because a giant slow kid is too gassed to get to the edge of the field quick enough). This is very rare at the pro level, because there are so many staff eyes on so many tiny aspects of each player and play to let this happen. So have a set (but not readable) system for pulling one or two players before they need to be pulled. In youth football, explain to the kids that rotations are intended to be before a kid is tired, and you expect hustle when the player is coming off the field. You don't want to hear, "Coach, I'm not tired" when you have a thousand other things on your mind.

The best way to sub is to send the new player in, and that player can immediately signal which position he is subbing. This is crucial, because you want both players heading in opposite directions at about the same time.

When it comes to penalties for substitutions, we can read the level of complexity being played. At the high school level (where coaches scheme to take advantage of young minds), penalties for "too many players on the field" are often because an offensve coordinator signals "hury up" to catch a slow defensive player trying to leave the field. At the pro-level, the problem is more often mis-communication (someone didn't come off the field at all).


This has been an overview of some of the factors that a defense considers when they are beaing worn down, or better, before they get to that point. If anyone has more detailed questions on this (or any other subject dealing with the game), drop them in the comments below. Remember, we're all family. No question is dumb. If you're just learning the game, or have been playing or coaching over the years, we'd love to hear from you.